1. Field of the Invention
The invention relates to a voltage protection arrangement for an electronic device, especially for a control in automation engineering.
2. Description of Related Art
Electronic devices, especially controls in automation engineering, require a certain DC voltage supply whose value may fluctuate only within a certain range. If the supply voltage is outside the specified voltage range, this can lead to faults in the electronic device, for example, improper operations, or incorrect reports of a control or even to destruction of the electronic device. Destruction of the electronic device or components of the electronic device can occur especially when an overvoltage is present. Therefore, the prior art discloses protecting sensitive and high-quality electronic devices against harmful overvoltages using voltage protection arrangements.
In the DC voltage range in which the voltage protection arrangement of this invention is primarily used, for this purpose, overvoltage protection circuits consisting of a fuse and a Z diode or a suppressor diode have been used in practice to date. If there is an overvoltage on such an overvoltage circuit, this leads to triggering of the fuse made generally as a fusible link, by which the electronic device to be protected is isolated from the voltage supply. The value of the overvoltage at which the overvoltage protection circuit responds can be fixed by the choice of a suitable Z diode or suppressor diode.
One fundamental disadvantage of such an overvoltage protection circuit consists in that the fuse for protection of the downstream electronic device is intentionally destroyed in the case of an overvoltage so that, after eliminating the overvoltage, the electronic device to be protected is isolated from the voltage supply. The electronic device is only serviceable again when the overvoltage protection circuit has been repaired beforehand, i.e., the fuse has been replaced.
In recent years, safety engineering in machine building and plant engineering has acquired growing importance. This results in additional demands for voltage protection and fault tolerance of control and other safety relevant electronic devices. In particular, it is required that machines and systems, in case of a fault, are transferred into the safe state so that a risk to individuals or the environment is avoided. Moreover, it is often desired that when a fault, for example, an overvoltage, occurs, not only is the electronic device to be protected turned off, but the fault is also reported.